1. Field of the Invention
This invention relates to energy absorbers for use in a fall protection system (FPS) to reduce the shock load acting on the anchorage of a horizontal lifeline of the FPS when the free fall of an object or person is arrested thereby within a fall distance determined by the FPS. More particularly, this invention relates to an energy absorber (EA) comprising a load carrying component which determines the ultimate strength of the EA and a plurality of energy absorbing components having selected breaking strengths and arranged to break sequentially when a shock load is imposed on the EA, to ensure that the force acting on the anchorage does not exceed a predetermined level.
2. Prior Art
Conventional FPS's for use by workers on construction sites comprise a safety harness worn by the worker and a short lanyard attached thereto at one end and at the other end to a vertical lifeline (VLL) anchored at its highest point to the structure being worked on or to a permanent horizontal lifeline (HLL) installed outdoors and extending between two anchorages.
In many applications, for example power line maintenance, the structure being worked on will present a number of projecting members which could seriously injure a falling worker if he or she were not brought to a stop within a short distance. Safety regulations of the Province of Ontario allow a maximum permissible free fall distance in FPS's of 1.5 m.
In order that the peak arresting force on the individual using an FPS not exceed a level which would be physically injurious when the lanyard is fully extended at the end of the fall, it is well known to include a shock absorber positioned between the lanyard and a harness to absorb the kinetic energy generated by a worker falling the limiting distance. An example of such a shock absorber is shown in U.K. patent application No. 2,136,915 published Sept. 26, 1984.
Conventional shock absorber devices are designed to lower the maximum arrest force (MAF) acting on the user of an FPS. It is desirable, particularly for use in conjunction with a permanent HLL system, that energy absorbing means be incorporated within the lifeline itself to reduce the maximum arrest load (MAL) acting on the anchorages of the horizontal lifeline. Known "personal" FPS shock absorbers of the kind utilizing breakable stitching within webbing to absorb shock would not be suitable for installation on a permanent HLL system, because of the susceptibility to degradation of the constituent materials by weathering and the different force levels at which such shock absorbers operate.
It is accordingly one object of the present invention to provide an EA for installation in an HLL system to reduce the MAL acting on the lifeline anchorages to acceptable levels.
It is a further object of the invention to provide an EA as aforesaid which is of simply, durable construction and is easily maintained.